Most commercially available synthetic polymers have electrical insulating characteristics, i.e. they are dielectric materials. As a result, finished products made from such polymers, such as phonograph records or disks, often develop strong static electrical charges when subjected to mechanical friction, whereby dust and dirt particles are attracted thereto and held thereon.
It has already been a past practice subsequently to finish synthetic fibers with various antistatic substances in order to combat the aforementioned phenomena. Various surfactants, including anionic, cationic, and nonionic known organic surfactants have been used as such antistatic substances.
It has further often been proposed to mix plastic molding compositions with antistatic substances with the objective of obtaining plastic products with permanent, built-in, antistatic properties. See, for instance, DE-AS 1 215 925, DE-OS 15 44 670, DE-AS 23 41 950, and U.S. Pat. No. 2,978,440. However, antistatic agents have only a limited compatibility with conventionally used organic polymer plastics, such as polyvinyl chloride (PVC). As a result the added antistatic agents at least partially migrate to the surface of the ultimately-formed object, which is accompanied by the formation of a thin surface film. Plastic products produced from such plastic materials, as by compression molding, then have a reduced tendency to acquire an electrostatic charge because water from air is sorbed onto this surface film and together with the antistatic agent is able to dissipate the static charge.
However, the quality of an antistatic finish in other respects is particularly critical in the case of various molded objects, and especially so in the case of phonograph records made from PVC-vinyl acetate (VA) copolymers. Attempts have already been made to produce in this manner antistatically-finished phonograph records. See, for instance, Soviet Pat. No. 870,416 (C.A., vol. 96, 105239v), Soviet Pat. No. 891,715 (C.A., vol. 96, 182280d), and EP-PS 10975. However, these various past attempts have failed under practical conditions, probably mainly due to the fact that the surface film of antistatic substances has an irregular thickness and tends to be formed in a droplet-like manner rather than as a smooth contiguous surface film. As a result, phonograph records produced in this fashion exhibit an increased background noise level during playback which is unacceptable under present day standards for phonographic recordings. In addition, the irregular thickness of the surface film does not provide uniform charge dissipation and when molding such materials, there tends to be a surface depletion of the antistatic agent. Surface resistance values of 10.sup.11 to 10.sup.12 .OMEGA. have been measured. This means that the discharge half-life of the electrostatic charges is in the range of minutes so that there is no question of having achieved an effective antistatic finish on the molded product.
Through the use of special compounding processes, providing a particularly complete homogeneous distribution of the necessary high antistatic agent quantities, it is possible to obtain a granular material from which it is possible to compression mold phonograph records having a surface resistance in the range of 10.sup.8 to 10.sup.9 .OMEGA. and a discharge half-life of below 1 second. However, the disadvantage of this procedure is that all of the molding composition components must pass through this complicated compounding stage and, in general, the phonograph record manufacturer does not generally have such equipment.